Development of a watermark such that when data of audio contents or video contents is recorded onto a recording medium, the watermark is embedded as additional information by multiplexing copy management information into the data of the contents for the purpose of protecting a copyright is being advanced. As such a watermark, there are known: a method of inserting the additional information into lower bits of a signal or a high-order coefficient at the time of compression; a method of inserting the additional information by using a masking effect lest the contents is influenced; a method of dispersing a spectrum of the additional information by using a spread spectrum and multiplexing them into the data of the contents; a method of inserting the additional information into a first peak, a second peak, or a location near the first or second peak in a predetermined range; and the like.
In music contents, record companies, computer engineering companies, communication equipment companies, and the like gather and are engaged in an activity called SDMI (Secure Digital Music Initiative).
They are continuing the activity for the purpose of preventing illegal distribution of the music contents via the Internet or the like or an illegal copy of the distributed music contents.
In the SDMI, there is a method of inserting copyright management information into the information of the contents by using a watermark which can be detected even in a state of an analog signal.
It is desirable to insert the watermark in a manner such that there occurs no auditory problem and the watermark is not easily erased even if an A/D conversion or a D/A conversion is repeated or compressing and decompressing processes are repeated.
However, such a powerful watermark that it is not easily erased even if an A/D conversion or a D/A conversion is repeated or compressing and decompressing processes are repeated cannot be easily rewritten. It is, therefore, difficult to make fine management such as generation management of the copy.
That is, as copy management information for protection of the copyright, an SCMS (Serial Copy Management System) is used with respect to the music contents. According to the copy management information of the SCMS, the copy is managed by using information of two bits.
According to the copy management information of the SCMS, not only a copy free and a copy inhibition but also copy management over the generation such as “copy of 1-generation is possible” can be performed. For example, according to the SCMS, the copy of 1-generation is possible when the copy management information SCMS of the original is equal to (0, 1). In this case, when the original information in the recording medium is copied into another recording medium, it is necessary to rewrite the copy management information SCMS from (0, 1) indicative of “copy of 1-generation is possible” to (1, 1) indicative of “copy inhibition”.
In case of a watermark of weak intensity such that by executing signal processes such as compressing/decompressing processes or the like, at least a part of it is erased or a part of the information is dropped, rewriting of the watermark can be relatively easy. According to such a watermark of weak intensity, however, there is a problem such that when the copy of the information is repeated, the information of the watermark is erased and the copyright cannot be protected.
It is, therefore, an object of the invention to provide a recording medium, a recording and/or reproducing method of the recording medium, and a data copying method, in which when data of contents is protected by using information of a watermark, finer copyright management can be made and it is also possible to cope with erasure of the watermark in association with repetition of a copy.
Another object of the invention is to provide a recording medium, a recording and/or reproducing method of the recording medium, and a data copying method, in which copy management by generation management can be made without rewriting a watermark.